The purpose of the proposed research is to find out whether there is a turnover of calcium in the otoconia, to quantitate the rate of the calcium uptake, and to investigate to what extent the calcium metabolism is altered by ototoxic drugs and by changes in the systemic calcium balance. Otolithic membranes are dissected out in toto and the Ca45 is measured by liquid scintillation spectrometry count. Guinea pigs and gerbils will be given streptomycin, gentamicin, and neomycin and the possible effects of drugs administration of the Ca45 uptake and decay will be determined. Previous experiments with ototoxic drugs in our laboratory show that neomycin will affect, in addition to the cochlea, only the macula sacculi while streptomycin will involve both maculae, but cause the most severe degenerative changes in mucula utriculi. It is therefore hoped that by using these two drugs selective changes in the Ca45 uptake and decay can be demonstrated in each macula. In the final phase of the experiment the effect of a negative calcium balance on the uptake will be studied. Hyperparathyroidism, possibly immobilization and aging are the means planned for creating this condition. BIBLIOGRAPHIC REFERENCES: Preston, R.E., Johnsson, L-G., Hill, J.H., and Schacht, J.: Incorporation of radioactive calcium into otolithic membranes and middle ear ossicles of the gerbil. Acta Otolaryngol. 80: 269-275, 1975. Ross, M.D., Johnsson, L-G., Peacor, D., and Allard, L.F.: Observations on normal and degenerating human otoconia. Ann. Otol. 1976 (In press).